The investigators propose that estrogens induce expression of proteins in coronary smooth muscle which inhibit the smooth muscle proliferation associated with atherogenesis. Their study aims to identify these estrogen-induced proteins via molecular techniques, utilizing smooth muscle cells from men & postmenopausal women not on HRT after exposing the cells to estrogen. Based on the findings, levels of mRNA's will be measured in men and postmenopausal women not on HRT & compared to levels in postmenopausal women on HRT or premenopausal women.